Method for cementing and testing wells



Oct. 8, 1935. w. L. C URCH 2,016,919

METHOD FOR CEMENTING AND TESTING WELLS Filed May 15, 1934 I I I"Patented Oct. 8, 1935 UNITED STATES PATENT OFFICE Walter L. Church,Houston, Tex.

Application May 15, 1934, Serial No. 725,739

.. 4 Claims.

This invention relates to a methodior cementing and testing wells.

It is often desirable to cement around a casing or pipe in a well boreto separate one stra- 5 tum from another and particularly to form abarrier between the water bearing and oil bearing strata. It is commonpractice to force plastic cement down through the casing or pipe to becemented and out through an outlet into the space between the casing orpipe and the walls of the bore. This is commonly done by entrapping theplastic cement between a lower and an upper plug in the casing and thenforcing the cement downwardly to the point of discharge by theapplication of fluid under pressure to the upper plug. When the lowerplug passes beneath the outlet, at the point where the cementing is tobe done, the upper plug is forced on downwardly to force the load ofcement out through said outlet and the cement rises around the casinguntil the upper plug is stopped by the lower plug and no more cement canthen be forced out. When this method is employed, it

often happens that the cement arising around the casing does not form acomplete barrier but channels are left therein through which the wateror gas or oil can pass from one stratum to another. Furthermore,inasmuch as the .cross sectional area of the bore between the pipe to becemented and the walls of the bore is usually greater than the crosssectional area of inside of the pipe a sufiicient quantity of cement cannot be forced, by the ordinary method, down through the pipe andreturned back up on t 6 outside of the pipe or casing to the level desred to cement around the upper portion of said pipe or casing.

It is an object of this invention to provide a method whereby the cementmay be forced down around the inner pipe from top to bottom and into thelower end thereof whereby the inner pipe may be cemented from top tobottom of the pipe to be cemented and the cement may rise within theinner pipe the desired distance.

Another object is to provide amethod whereby a string of pipe or casingmay be floated into the well by the use of afloat shoe which is closedagainst the inlet of liquid while the string is being lowered but whichmay be opened when the string reaches the bottom so that the liquid inthe well may be forced out through the string by fluid pressure as thecementitious materialis being forced into the bore around the string ofpipe and the space between said string and the walls of the bore fromthe upper to the lower end of the string may be filled with cementwhereby the entire string may be cemented to prevent gas escaping fromlower strata and entering the shallower water sands and charging saidlast mentioned sands with gas which other- 5 wise would later blow outafter the completion of the well, to injure or destroy the well.

Another object of the invention is to provide a novel method for testingwells in unproven fields and by the use of which a well can be 10drilled to the maximum depth desired and the different strata havingproducing possibilities accurately located and a string of pipe then setin the bore and cemented on the outside and after the cement has set thestring then per- 15 forated opposite the lowermost stratum and if oil benot found therein the inside of the casing then cemented up to the nextstratum supposed to contain oil or gas and the pipe again perforated andsaid stratum tested; the different 20 strata thus being tested from thelowermost one upwardly until a producing stratum is found or the well isabandoned. At the present time in drilling wells when a stratum isencountered supposed to contain 011, the casing is set on top 25 of saidstratum and the hole is reduced and bored into the stratum and pipe ofsmaller diameter is then set and if oil in paying quantities is notfound the smaller pipe must be moved in order to resume drillingoperations and this proc- 30 ess must be repeated as the differentstrata are reached supposed to contain oil, until the well is completedor abandoned. The method of testing herein described and claimed is muchsimpler and not so expensive as the method now 35 commonly used as aboveidentified.

The method of cementing herein described and claimed may be employed forcementing a string of pipe from the upper to the lower end thereof orfrom any selected point as at a point above 40 the well screen to thetop of the well.

With the above and other objects in view the invention has particularrelation to a novel method an example of which is given in thisspecification and illustrated in the accompany- 45 ing drawing, wherein:V

Figure 1 shows a fragmentary vertical sectional view partly in sectionshowing the string lowered to the bottom of the bore preparatory tocementing the same. 50

Figure 2 shows a fragmentary vertical sectional view showing the lowerend of the string cemented throughoutthe length thereof and perforatedopposite the strata to be tested, and a Figure 3 shows a side elevationof the string of pipe located and cemented in the well and perforatedopposite the strata and showing the string plugged up above anon-producing stratum.

In the drawing the numeral I designates the surface casing and thenumeral 2 designates a string of easing or pipe, which extends to thebottom of the well. Attached to the upper end of the surface casing Ithere is a conventional type of braden head I through which the string 2extends, said braden head closing the space between the surface casing Iand the inner casing 2. A float shoe designated generally by the numeral3 is attached to the lower end of the casing 2. This float shoe containsa valve cage 4 which confines the ball valve 5 and above said valveswithin the float shoe there is an\ annular valve seat I. As

the inner casing or pipe 2 is lowered through the fluid in the well thevalve 5 will be held in posi tion to close the seat 6 to prevent theentrance of drilling fluid from the well into the casing 2. The,

seat 6 forms the lower end of a nipple I which is of tubular formation,having the central axial water course I therethrough, which dividesforming the side passageways 0, 8 into the interior of the string 2. Theupper end of the passageway 8 is reduced forming a bearing III and aninside annular shoulder II. A plunger I2 is slidablymountedinthe-bearing I0 andhasahead It on its upper end. A latch I4 isseated in a countersunk vertical groove in one side of said plunger andis pivoted therein at its lower end. The upper end of said latch is freeand is seated against a coil spring I5. While the string 2 is beinglowered the plunger I2 is in upper or inactive position but when saidstring is landed on bottom a plug as I6 may be forced by fluid pressuredown through the string 2 and the plug will engage the head It and forcethe plunger l2 downwardly against the valve 5 to unseat the same andwhen the upper end of the latch clears the shoulder I I the spring I!will force said latch outwardly and cause it to engage said shoulder asto latch the plunger I2 in its lower or active position whereby thevalve 5 will be secured in its lowermost, or open, podtion. Water maythen be forced into the space between the surface casing I and the innercasing 2, through the inlet pipe I! which is screwed into the bradenhead I, and the plug II thereby forced back up through the casing 2 tothe ground surface. A sufllcient amount of clean water may be forceddown through the bore on the outside of the pipe 2 and back up throughsaid pipe to wash the well. Cementitious material may then be forcedinto the well bore around the inner pipe through the pipe I! by theapplication of pressure thereto and as said material is forceddownwardly the fluid in the bore will be forced downwardly aheadof it,and will pass up through the inner pipe 2. This process is continueduntil the bore from the top to bottom around the inner pipe is filledwith cement and a 'sufiicient amount of the cement is forced into thelower end of the inner pipe to fill the lower end thereof beneath thelower stratum to be tested. The cement is then allowed to set or harden.

After the cement has sumciently set a perforating tool may be loweredthrough the inner pipe and said pipe and the surroundingcement-perforated opposite the lower stratum. As previously stated eachstratum has been located during the drilling of the bore so that theperforations can readily be made opposite the stratum which it isdesired to test. If the tested stratum proves to be a producing stratumthe well can then be completed in the usual way but if it should notprove to be a producing stratum plastic cement can be lowered throughthe inner pipe and the same can be cemented up above the perforatedsection and the inner pipe can then be perforated opposite the nextsucceeding stratum above until a producing stratum is discovered or thewell abandoned.

-The inner pipe is thus completely and effectively cemented from the topthereof down to the bottom of the bore so as to effectively seal offeach stratum from the others.

Cementitious material will ordinarily be employed for the purposespecified but it is to be understood that in carrying out the processother suitable materials may be employed such as barite or any otherheavy material which may be reduced to a fluid state so that it may bepumped into the well and which will pack around the inner pipe to asufilcient density to become impervious to the passage of liquidtherethrough and the term cement or cementitious material as used hereinis intended to be construed to include any plastic material or'fluidsolution of 25 such a nature as to be readily forced into the well underpressure and to set or pack about the inner pipe so as to form acontinuous seal around said inner pipe to prevent the passage of liquidfrom one stratum to another in the well.

What I claim is:

1. The process of testing strata in a well which consists in locating apipe in the well, forcing a sealing material into the well around thepipe,

allowing the material to set to form a continuous 35 seal from a pointbeneath to a point above the strata, perforating the pipe and sealopposite the various strata to be tested from the lowermost upwardly,closing the perforations opposite a stratum beneath prior to perforatingopposite 40 a stratum above.

2. In completing a well the process which comprises lowering a pipe,having a normally closed inlet, into the well, opening said inlet,forcing a sealing material into the space between the pipe 4 stratawhich walls of the well to flll said space a selected distance along thepipe and to close the lower end of the pipe, allowing said material toset, perforating the pipe and seal at points opposite the strata to betested in succession from below upwardly, closing the perforations atone stratum prior to perforating at the next succeeding stratum.

4. The process of testing strata in a well which consists in locating apipe in the well, delivering a sealing material into the well about thepipe,

allowing the material to set to form a continuous seal from a pointbeneath to a point above the strata, perforating the pipe and sealopposite the various strata to be tested from the lowermost upwardly,closing the perforations opposite a.

stratum beneath prior to perforating opposite a stratum above.

WALTER L. CHURCH.

